Thoughts filed in: Computing

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15
Apr

Self-referencing symlinks can hang your IDE

One of my current Drupal projects has been giving me a headache lately, due to a small but very annoying problem. My PHP development tools of choice, at the moment, are Eclipse PDT and TextMate. Both of these generally work great for me. I prefer TextMate if I have the choice (better config options + much more usable), but I switch to Eclipse whenever I need a good debugger (or a bit of contextual help / autocomplete). However, they haven't been working well for me in this case. Every time I try to load in the source code for this one particular project, the IDE either hangs indefinitely (in Eclipse), or it slows down to a crawl (in TextMate). I've been tearing my hair out, trying to work out the cause of this problem, which has forced me to edit individual files for several weeks, and which has meant that I can't have a debugger or an IDE workspace for this project. Finally, I've nailed it: self-referencing symlinks are the culprit.

The project is a Drupal multisite setup, and like most multisite setups, it uses a bunch of symlinks in order for multiple subdomains to share a single codebase. For each subdomain, I create a symlink that points to the directory in which it resides; in effect, each symlink points to itself. When Apache comes along, it treats a symlink as the "directory" for a subdomain, and it follows it. By the time Drupal is invoked, we're in the root of the Drupal codebase shared by all the subdomains. Everything works great. All our favourite friends throw a party. Champagne bottles pop.

The bash command to create the symlinks is pretty simple — for each symlink, it looks something like this:

ln -s . subdomain

Unfortunately, a symlink like this does not play well with certain IDEs that try to walk your filesystem. When they hit such a symlink, they get stuck infinitely recursing (or at least, they keep recursing for a long time before they give up). The solution? Simple: delete such symlinks from your development environment. If this is what's been dragging your system down, then removing them will instantly cure all your woes. For each symlink, deleting it is as simple as:

rm subdomain

(Don't worry, deleting a symlink doesn't also delete the thing that it's pointing at).

19
Mar

Deployment and migration: hot at DrupalCon DC

There was no shortage of kick-a$$ sessions at the recent DrupalCon DC. The ones that really did it for me, however, were those that dealt with the thorny topic of deployment and migration. This is something that I've been thinking about for quite a long time, and it's great to see that a lot of other Drupal people have been doing likewise.

The thorniness of the topic is not unique to Drupal. It's a tough issue for any system that stores a lot of data in a relational database. Deploying files is easy: because files can be managed by any number of modern VCSes, it's a snap to version, to compare, to merge and to deploy them. But none of this is easily available when dealing with databases. The deployment problem is similar for all of the popular open source CMSes. There are also solutions available for many systems, but they tend to vary widely in their approach and in their effectiveness. In Drupal's case, the problem is exacerbated by the fact that a range of different types of data are stored together in the database (e.g. content, users, config settings, logs). What's more, different use cases call for different strategies regarding what to stage, and what to "edit live".

Read on to find out about:

  • Context, Spaces and Exportables
  • Deploy module
  • Other solutions presented
  • How we've come a long way
17
Oct

Listing every possible combination of a set

The problem is simple. Say you have a set of 12 elements. You want to find and to list every possible unique combination of those elements, irrespective of the ordering within each combination. The number of elements making up each combination can range between 1 and 12. Thanks to the demands of some university work, I've written a script that does just this (written in PHP). Whack it on your web server (or command-line), give it a spin, hack away at it, and use it to your heart's content.

14
Oct

A count of Unicode characters grouped by script

We all know what Unicode is (if you don't, then read all about it and come back later). We all know that it's big. Hey, of course it's big: its aim is to allow for the representation of characters from every major language script in the world. That's gotta be a lot of characters, right? It's reasonably easy to find out how many unicode characters there are in total: e.g. the Wikipedia page (linked above) states that: "As of Unicode 5.1 there are 100,507 graphic [assigned] characters." I got a bit curious today, and — to my disappointment — after some searching, I was unable to find a nice summary of how many characters there are in each script that Unicode supports. And thus it is that I present to you my count of all assigned Unicode characters (as of v5.1), grouped by script and by category.

24
Sep

Randfixedsum ports in C# and PHP

For a recent programming assignment that I was given at university, I was required to do some random number generation. I decided to write my program in such a way that it needed a set of random numbers (with a fixed set size), each of which had to be within a fixed range, and all of which had to add up to a fixed total. In other words, what I needed was a function that let me say: "give me 50 random numbers, and make sure that each of those numbers is between 1 and 20, and also make sure that the total of all those numbers is 200... and remember, despite all that, they have to be random!" Only problem? Finding a function that returns such data is extremely difficult.

Fortunately, I stumbled across the ingenious randfixedsum, by Roger Stafford. Randfixedsum — as its name suggests — does exactly what I was looking for. The only thing that was stopping me from using it, is that it's written in Matlab. And I needed it in C# (per the requirements of my programming assignment). And that, my friends, is the story of why I decided to port it! This was the first time I've ever used Matlab (actually, I used Octave, a free alternative), and it's pretty different to anything else I've ever programmed with. So I hope I've done a decent job of porting it, but let me know if I've made any major mistakes. I also ported the function over to PHP, as that's my language of choice these days. Download, tinker, and enjoy.

27
Aug

Legislation and programming: two peas in a pod

The language of law and the language of computers hardly seem like the most obvious of best buddies. Legislation endeavours to be unambiguous, and yet it's infamous for being plagued with ambiguity problems, largely because it's ultimately interpreted by subjective and unpredictable humang beings. Computer code doesn't try to be unambiguous, it simply is unambiguous — by its very definition. A piece of code, when supplied with any given input, is quite literally incapable of returning inconsistent output. A few weeks ago, I finished an elective subject that I studied at university, called Legal Method and Research. The main topic of the subject was statutory interpretation: that is, the process of interpreting the meaning of a single unit of law, and applying a given set of facts to it. After having completed this subject, one lesson that I couldn't help but take away (being a geek 'n' all) was how strikingly similar the structure of legislation is to the structure of modern programming code. This is because at the end of the day, legislation — just like code — needs to be applied to a real case, and it needs to yield a Boolean outcome.

05
Jun

Drupal and Apache in Vista: some tips

I bought a new laptop at the start of this year, and since then I've experienced the "privilege" pile of festering camel dung that is being a user of Windows Vista. As with most things in Vista, installing Drupal and Apache is finickier than it used to be, back on XP. When I first went through the process, I encountered a few particularly weird little gotchas, and I scribbled them down for future reference. Here are some things to look out for, when the inevitable day comes in which you too will shine the light of Drupal upon the dark and smelly abyss of Vista:

  1. Don't use the stop / start / restart Apache controls in the start menu (start > programs > Apache > control), as they are unreliable; use services.msc insetad (start > run > "services.msc").
  2. Don't edit httpd.conf through the filesystem — use the 'edit httpd.conf' icon in the start menu instead (start > programs > Apache > configure), as otherwise your saved changes may not take effect.
  3. If you're seeing the error message "http request status - fails" on Drupal admin pages, then try editing your 'c:\windows\system32\drivers\etc\hosts' file, and taking out the IPv6 mapping of localhost, as this can confuse the Windows mapping of 127.0.0.1 to localhost (restart for this to take effect).
  4. Don't use Vista! If, however, you absolutely have no choice, then refer to steps 1-3.
09
Mar

The Net, ten years ago

Internet access is available anywhere these days — even on tropical islands in south-east Asia. Several weeks ago, I was on the island of Ko Tao in southern Thailand. Myself and several of my mates were discussing our views on the price of Internet usage. Most of us were in agreement that the standard Ko Tao rate of 2 baht per minute (about AUD$5 per hour) — which was standard across all of the island's many caf├ęs — was exhorbitant, unacceptable and unjustifiable. One bloke, however, had visited the island ten years previously. He thought that the rate was completely fair — as he remembered that ten years earlier, the entire island had boasted only a single place offering access; and that back then, they were charging 60B/min! Nowadays, the standard rate in most parts of Thailand is about ½B/min, or even ¼B/min if you know where to look. This massive price difference got me thinking about what else regarding the 'Net has changed between 1998 and 2008. And the answer is: heck, what hasn't?

24
May

An undo button for Drupal

Every time that you perform any action in a desktop application, you can hit the trusty 'undo' button, to un-wreak any havoc that you may have just wreaked. One of the biggest shortcomings of web applications in general, is that they lack this crucial usability (and arguably security) feature. However, implementing an 'undo' (and 'redo') system in Drupal should be a relatively simple task - much simpler, in fact, than you might at first think.

07
Oct

A plain-text program design standard

I've been working on a project at University, in which my team had to produce a large number of software design documents, which now have to be translated into working code. Wouldn't it be great if I could write just one design specification, and if from that, numerous diagrams and skeleton code could all be auto-generated? What the world needs is a plain-text program design standard.

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